Vibrating bed developing apparatus with electromagnetic developer agitator

ABSTRACT

Apparatus for developing electrostatic latent images carried by a support medium with a vibrating bed of two-component magnetizable developer material. The development unit includes a housing, containing developer material, positioned adjacent a latent image-bearing support medium and vibrated to convey the developer material into contact with the latent image for effecting the development thereof. A plurality of electromagnets are carried by the inner peripheral surface of the developer housing and sequentially actuated to, in combination with the vibratory movement effect intermixing of the developer material.

United States Patent Inventor Eugene F. Young Henrietta, N.Y. 854,838

Sept. 3, 1969 Oct. 12, 1971 Xerox Corporation Rochester, N.Y.

Appl. No. Filed Patented Assignee VIBRATING BED DEVEEOPING APPARATUS WITH ELECTROMAGNETIC DEVELOPER AGITATOR 4 Claims, 3 Drawing Figs.

US. Cl 118/623, 118/637,117/17.5

Int. Cl G03g 13/00 Field of Search 118/621,

References Cited UNITED STATES PATENTS 12/1970 Masamichi Sato 2,318,571 5/1943 Carlton 118/627 X 3,117,891 1/1964 Lehmann 118/637 3,357,399 12/1967 Fisher 118/637 3,484,265 12/1969 Swyler l l7/l7.5

Primary ExaminerMervin Stein Assistant Examiner-Leo Millstein AttorneysPaul M. Enlow, Donald F Daley, James J.

Talabate, Norman E. Schrader, Ronald Zibelli and August E. Roehrig, .lr.

ABSTRACT: Apparatus for developing electrostatic latent images carried by a support medium with a vibrating bed of two-component magnetizable developer material. The development unit includes a housing, containing developer material, positioned adjacent a latent image-bearing support medium and vibrated to convey the developer material into contact with the latent image for effecting the development thereof. A plurality of electromagnets are carried by the inner peripheral surface of the developer housing and sequentially actuated to, in combination with the vibratory movement cf fect intermixing of the developer material.

PATENTEU our 1 am $61 1. 991

SHEET 2 OF 2 VIBRATING BED DEVELOPING APPARATUS WITH ELECTROMAGNETIC DEVELOPER AGITATOR BACKGROUND OF THE INVENTION This invention relates in general to the development of electrostatic latent images on a support medium and, in particular, to eliminating development defects in a developing apparatus utilizing vibrational forces to apply developer material to the latent image.

More specifically, this invention relates to a vibrating bed developing apparatus having a plurality of electromagnets which are sequentially actuated to, in combination with the vibratory forces, effect the intermixing of the developer material within the developer housing to eliminate development defects resulting from localized developer conditions.

In the development of electrostatic latent images, developer material, which generally comprises a mixture of suitable pigmented or dyed resin-based powder (referred to as toner) and a carrier material, which functions to generate triboelectric charges on and to carry the toner, is applied to the latent image to render it visible. The developer material is brought into surface contact with the electrostatic latent image to render it visible. The developer material is brought into surface contact with the electrostatic latent image and the toner powder, for example of the type disclosed in Carlson U.S. Pat. No. 2,940,934,is removed from the carrier material and attracted to the latent image in a pattern corresponding to the electrical charges. Thereafter the developed toner powder image may be transferred to a support medium to which it may be permanently fixed or it may be fixed to the original electrostatic latent image bearing surface depending upon the particular electrostatographic imaging process utilized, as is well known in the art. In certain applications, it is desirable to effect development of electrostatic latent images through the 7 use of a toner carried by a magnetizable carrier medium coated with a material removed in the triboelectric series from the toner so that a triboelectric bond is generated between the toner and carrier material.

One method of developing electrostatic latent images is referred to in the art as vibrating of fluidized bed development. In such a development system, a quantity of two-component developer material is vibrated beneath the latent electrostatic image so rapidly that the developer material is suspended in a fluidized mass or bed. As an electrostatic latent image is passed through the development zone, the image is contacted by the vibrating or constantly moving developing to effect development of the latent images. Various fluidized or vibrating bed development techniques have been disclosed, for example, in US. Pat. Nos. 3,008,826; 3,380,437; and 3,393,663, These patents describe systems designed to enhance development of the electrostatic latent images by minimizing the mass of the fluidizing apparatus and enhancing image development through the use of development electrodes suspended in the vibrating bed developer housing.

Various development defects, due to localized developer conditions, have been associated with vibrating bed developing systems and a problem has existed in providing for the addition of toner powder depleted through the development of the latent images on the adjacent support surface. These development defects are referred to as image striations (wherein underdeveloped strips are observed across the image generally perpendicular or transverse to the movement of the latent image bearing surface) and tracking (wherein unwanted development streaks occur along the direction of movement of the latent image due to the developer material moving in a constant linear path relative to the latent image).

Striations, which are caused by an uneven contacting of the image-bearing surface by the developer material, occur most predominantly in fluidized bed development systems which vibrate the developing material in the direction of the image movement. These striations are caused by the slapping effect that waves of fluidized developer material have on the imagebcuring surface. As an image-bearing surface is moved through the vibrating developer, it is rhythmically contacted by these fluidized bed developer waves. This periodic contact of these latent image-bearing surface by the developer material creates an uneven developer presentation to the image which causes image striations. Tracking, or unwanted developer streaks in the direction of movement of the latent image, occurs when a quantity of developer material includes a mass of undertoned carrier particles or carrier particles which have been depleted of toner such that the mass of carrier is presented along one line of the latent image-bearing surface until it is replaced by properly toned carrier flowing through the developer zone. If the developer material and latent image bearing surface move in a straight line relative to each other, the improperly developed image portion will be extended over a straight line the length of the latent image area.

Certain ones of these development defects have been minimized by vibrating bed developing apparatus which is vibrated in a direction transverse of the electrostatic latent image support medium 3 s path of movement. However the problem of intermixing developer material to eliminate developer tracking and to minimize image striations, along with adding toner powder to the developer mixture as the electrostatic latent images are developed, remain considerations considerations in a developing system.

As toner powder is added to the developer mixture, the mixture must be throughly intermixed to create the desired triboelectric relationship between the toner powder and the carrier material. This maintenance of the proper triboelectric relationship between the materials of the developer mixture becomes increasingly important when the movement of the developer material is limited as in a vibrating bad-developing system. Therefore, it becomes necessary for the cross-mixing and intermixing of the developer material to eliminate development defects characteristic of localized developer conditions such as occurs when a multiple number of copies are reproduced from a single original. If the developer mixture is not intermixed, developer material in certain areas will have a high concentration of toner powder than other areas resulting in a nonuniform toner powder image.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention to improve apparatus for developing latent electrostatic images.

Another object of this invention is to increase the intermixing and cross-mixing of developer material in a vibrating bed developing apparatus.

A further object of this invention is to eliminate development defects characteristic of localized developer conditions.

Still another object of this invention is to utilize the vibratory forces of a vibrating bed developing system to minimize the external forces required to intermix the developer material.

These and other objects are attained in accordance with the present invention wherein there is provided a vibrating bed developing system utilizing a two-component magnetizable developer material wherein the vibrational force is applied so rapidly that the mass of developing material will be suspended to contact and develop images on the surface. A plurality of sequentially actuated electromagnets are positioned about the inner peripheral surface of the vibrating bed developing unit to, in combination with the vibrational forces, intermix the developing material contained in the developer housing.

Further objects of the invention, together with additional features contributing thereto and advantages accruing therefrom, will be apparent from the following description of one embodiment of the invention when read in conjunction with the accompanying drawings BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a mechanical schematic representation of an automatic xerographic reproducing machine utilizing the invention of this application;

FIG. 2 is a front perspective view of a vibrating bed development apparatus to better illustrate the positioning of the electromagnets within the developer housing; and

FIG. 3 is an electrical-mechanical schematic of the electromagnetic development intermixing system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 11, there is illustrated a mechanical schematic of an automatic xerographic reproducing apparatus embodying the present invention. The elements of this machine are all well known in the electrostatographic art with the exception of the development station which forms the basis of the present invention. For convenience of illustration the vibratory movement of the developer mechanism 410 is described as transverse to the movement of the electrostatic latent image-bearing support surface. However, it is not intended to be so limited but may be utilized wherein the vibratory movement is radial or parallel to the movement of the latent image bearing surface, or any other such vibratory movement.

An electrical charge pattern is formed on the surface of the drum 1 by any suitable technique, for example, as illustrated in FIG. I by charging and exposing a photoconductive surface. The latent image is subsequently rendered visible at a developing station 41 and then may be transferred 5 to a suitable support medium 6 to which it is permanently affixed or the image may be permanently affixed to the image support surface depending upon the type of photoreceptor used as is well known in the electrostatographic art.

The developing apparatus shown in FIG. 1 is constructed in two major sections, a developer vibrating or developing assembly 40 and the developer recirculation assembly 80. The purpose of the developer vibrating assembly is to impart vibratory motion to magnetizable two-component developer material adjacent the electrostatic latent image bearing surface. The developer recirculation assembly is to move developer to the input of the developer vibrating elements and returned to the sump portion 81 of the developing apparatus.

The developer vibrating assembly, 40, best illustrated in FIG. 2, comprises an arcuate plate 41 positioned concentric with the photoreceptor and spaced therefrom to rapidly vibrate the developer material against the electrostatic latent image. The opposite ends of the arcuate plate 41 are secured by suitable means to a mounting plate 42 positioned adjacent the opposite end faces of the drum. The mounting plates are provided at each end with suitable guide pins 43 and apertures 14 which restrain the arcuate plate and the rest of the vibratory elements for movement in a purely reciprocatory longitudinal path.

A screen 50 is secured concentric with and between the drum 1 and arcuate plate 41 for aiding in vibrating the developer material. The screen is grounded or provided with an electrical bias from any suitable source of potential to thus create an electric field adjacent the image and is suitably electrically isolated from the plate 51 by suitable insulation.

In order to guide the vibrated developer material in a return path towards the developer recirculation assembly $0, a plate 60 with a J-shaped cross section is also secured at its opposite end between the mounting plates &2. The plate 60 is thus vibrated with the arcuate plate 41 and screen 50 during operation for maintaining the developer in a fluidized state. The developer thus exhibits a movement down the longer leg 61 of the plate 60 toward the developer recirculation assembly 80 after reversing direction at the curved portion 62.

The developer recirculation assembly 80 is similar to the conventional unit employed to convey developer material from the sump portion of a cascade development unit to introduce the material to the latent image. A bucket conveyor assembly b5 comprising a plurality of buckets 86 supported on a flexible endless belt 87 is held in position by two suitably driven rollers 88 and 89. The conveying assembly circulates developer material from the sump 81 to be introduced to the latent image by the vibratory assembly :10. The vibratory mo tion to the developer assembly is imparted by a motor MOT-ll suitably connected to the vibratory mounting plates 42 and coupled whereby the rotary motion of the drive shaft is converted to a reciprocation of the vibratory elements.

For further information concerning the specific details of a suitable vibrating bed development apparatus as herein disclosed, reference is made to KJ. Swyler U.S. Pat. No, 3,380,437.

Referring now to FIGS. 2 and 3, there is shown a plurality of electromagnets supported along the inner peripheral surface of the developer vibrating assembly and electrically isolated from the developing vibrating assembly and electrically apparatus. The electromagnets are appropriately secured to the mounting plates 42, and front (62) portion of the J-shaped cross section plate 60 having its opposite ends secured between the mounting plates 42. The electromagnets 90 are connected through suitable electrical connections to a commutator COM1 and sequentially actuated by the rotation of the commutator arm 91. In operation, as the vibratory move ment is imparted to the developing assembly 40 the magnetizable developer material is vibrated in a suspended or fluidized mass. The electromagnets 90 are sequentially actuated by the commutator COM-ll such that as the developer material is vibrated in a suspended mass, the developer material is attracted towards the electromagnet which has been actuated by the commutator. In this manner the developer material is attracted in a direction towards the selectively actuated electromagnet and simultaneously applied to the latent electrostatic image. By a combination of the vibratory motion of the unit 40 and electromagnetic forces effected upon the sequential and mutually exclusive actuation of each of the electromagnets 90, the developer material is caused to flow in a somewhat circular motion thereby intermixing the developer material and eliminating localized development defects as the developer material is simultaneously vibrated and cross-mixed.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.

What is claimed is:

1. In an apparatus for developing latent electrical charges selectively retained in image configuration on a support medium by vibrating a developer supporting surface to create a suspended fluidized mass of magnetizable developer material with agitating movement in operative contact with the latent electrical charges, the improvement comprising,

mixing means supported by said developer supporting surface actuable to effect movement of the magnetizable developer material in a direction independent of the agitating movement of said developer material.

2. In an apparatus for developing latent electrostatic charge patterns on a support medium in which a developer reservoir containing a quantity of magnetically attractable developer material in communication with said support medium is vibrated to create a suspended fluidized mass of developer material in operative relation to said support medium, the improvement comprising,

electromagnetic means supported by said developer reservoir adapted when actuated to effect an intermixing movement of the suspended fluidized mass of developer material within said reservoir independent from any movement imparted to said developer material by the vibration of said developer reservoir.

3. Apparatus for developing latent electrostatic charge patterns on a support medium including,

a developing reservoir in communication with said support medium and containing a quantity of magnetically attractable developer material,

means for vibrating said developer reservoir to create a suspended fluidized mass of developer material in operative relation to said support medium, and

electromagnetic means supported by said developer reservoir adapted when actuated to effect an intermixing movement of the suspended fluidized mass of developer material within said reservoir independent from any movement imparted to said developer material by said vibrating means.

4. Apparatus for developing latent electrostatic charge patterns on a support medium including;

a vibratory developer reservoir in communication with said support medium and containing a quantity of magnetically attractable developer material,

means for rapidly vibrating said developer reservoir to create a suspended fluidized mass of developer material in operation relation to said support medium,

electromagnetic means supported by said developer reservoir adapted when actuated to elfect an intermixing movement of the suspended fluidized mass of developer material within said developer reservoir independent and exclusive of any movement and agitation imparted to said developer material by said vibrating means, and

means for periodically actuating said electromagnetic means to effect said intermixing movement of the suspended fluidized mass of developer material while in communication with said support medium and thereby enhance the development of said charge patterns on said support medium. 

1. In an apparatus for developing latent electrical charges selectively retained in image configuration on a support medium by vibrating a developer supporting surface to create a suspended fluidized mass of magnetizable developer material with agitating movement in operative contact with the latent electrical charges, the improvement comprising, mixing means supported by said developer supporting surface actuable to effect movement of the magnetizable developer material in a direction independent of the agitating movement of said developer material.
 2. In an apparatus for developing latent electrostatic charge patterns on a support medium in which a developer reservoir containing a quantity of magnetically attractable developer material in communication with said support medium is vibrated to create a suspended fluidized mass of developer material in operative relation to said support medium, the improvement comprising, electromagnetic means supported by said developer reservoir adapted when actuated to effect an intermixing movement of the suspended fluidized mass of developer material within said reservoir independent from any movement imparted to said developer material by the vibration of said developer reservoir.
 3. Apparatus for developing latent electrostatic charge patterns on a support medium including, a developing reservoir in communication with said support medium and containing a quantity of magnetically attractable developer material, means for vibrating said developer reservoir to create a suspended fluidized mass of developer material in operative relation to said support medium, and electromagnetic means supported by said developer reservoir adapted when actuated to effect an intermixing movement of the suspended fluidized mass of developer material within said reservoir independent from any movement imparted to said developer material by said vibrating means.
 4. Apparatus for developing latent electrostatic charge patterns on a support medium including; a vibratory developer reservoir in communication with said support medium and containing a quantity of magnetically attractable developer material, means for rapidly vibrating said developer reservoir to create a suspended fluidized mass of developer material in operation relation to said support medium, electromagnetic means supported by said developer reservoir adapted when actuated to effect an intermixing movement of the suspended fluidized mass of developer material within said developer reservoir independent and exclusive of any movement and agitation imparted to said developer material by said vibrating means, and means for periodically actuating said electromagnetic means to effect said intermixing movement of the suspended fluidized mass of developer material while in communication with said support medium and thereby enhance the development of said charge patterns on said support medium. 